Defense Secretary Ash Carter speaks to reporters during a joint news conference with British Defense Secretary Michael Fallon, Friday, Dec. 11, 2015, following their meeting at the Pentagon. (AP Photo/Manuel Balce Ceneta)

U.S. Defense Secretary Ash Carter urged Turkey on Tuesday to do more to help destroy Islamic State of Iraq and Syria (ISIS) militants as he kicked off a tour of the Middle East that aims to drum up regional support for the military campaign.

Speaking to reporters while traveling to the Incirlik air base in southern Turkey, Carter said Ankara needed to better control its border with Syria, particularly a roughly 60-mile (98-km) stretch believed to be used by ISIS for illicit trade and for shuttling foreign fighters back and forth.

“Turkey has an enormous role to play,” said Carter, on his first trip to Incirlik as defense secretary. “We appreciate what they’re doing. We want them to do more.”

That includes Turkish forces joining “in the air and the ground as appropriate,” Carter said. “The single most important contribution that their geography makes necessary is the control of their own border.”

Incirlik has grown more important in the U.S.-led campaign of air strikes against ISIS, with 59 U.S., Turkish, Qatari and German aircraft conducting refueling, intelligence, and strike missions now operating out of the base, up from about 15 from all coalition countries at the beginning of September, U.S. officials said.

That number is expected to increase in the coming weeks and months, though officials did not provide details.

Around 45 of the 59 aircraft using Incirlik are from the United States and include both manned and unmanned.

The United States has pushed for a more assertive Turkish contribution in fighting the Islamic State, particularly in securing the border with Syria, but also in seeing more Turkish air strikes devoted to ISIS.

On Monday, speaking after a meeting of the U.S. National Security Council at the Pentagon, President Barack Obama said Carter’s trip to the region aimed to secure greater military contributions from allies in the campaign against ISIS.

U.S. ‘must do more’ to counter ISIS propaganda

Meanwhile, the U.S. military’s top general warned on Monday that America is coming up far short in its efforts to counter ISIS propaganda, and the extremists’ messages often resonate with younger people.

“I think we probably do get a C-minus or D in terms of doing it right now,” General Joe Dunford told a national security forum in Washington.

Dunford, whose official title is Chairman of the Joint Chiefs of Staff, said people in the West tend to overlook the power of IS on social media – even as the extremists’ propaganda captures the imagination of some.

“What’s concerning to me is… the narrative that ISIL has is getting traction and we need to take that part of it serious,” he said, using an alternative acronym for the ISIS group.

“We can look at the absurdity of the ideas and immediately be dismissive. It’s easy to do but those ideas resonate,” he added.

“Amazingly enough they are resonating with young people here in the United States who are either disaffected, dislocated or just not fully integrated in our society.”

Dunford, who previously headed the Marine Corps, started his new role at the Pentagon at the end of September.

He appeared at a briefing earlier Monday with Obama, who voiced fresh determination to destroy the ISIS group, vowing to kill their leaders and win back territory in the Middle East.

The United States has since August 2014 been leading a coalition bombing the ISIS group in Iraq and Syria.

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